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(No Model.)

0. A. RANDALL.

TELBPHGNB EXGHANGE SYSTEM. No..270,566. Patented Jan. 9, 1883.

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CHARLES'IA. RANDALL, OF NEW YORK, N. Y.

TLPHON=XCHANG SYSTEM.

SPECIFICATION forming part of Letters Patent No. 270,556, dated January 9, 1883.

Application nieu october 1T, 1882.

Io all whom it may concern Be it known that I, CHARLES A. RANDALL, a citizen of the United States, residing at New York, in the county and State of New York, have invented new and useful Improvements in Telephone-Exchange Systems, ot which the following is a specification.

rIhis invention relates to a telephone-exchange system in which each subscriber-s station is connected with a central ofticeby two line-wires, its object being to provide a complete metallic circuit for subscribers when connected for conversation by telephone, and to utilize one line-wire ot' each subscriber for calling and conversation with the central oflice.

The invention consists in certain novel combinations ot' line-wires and apparatus at acentral ot'tice and subscribers stations, as will be fully hereinafter described.

1n the accompanying drawings, Figure 1 is a diagram illustrating the apparatus at the central office and two subscribers stations connected therewith. Fig.. 2 is a diametric section ofthe switch-board on line x .t ot' Fig. l, and Figs. 3 and 4 are modifications of the connector and socketed connections therefor.

rlhe devices at the central office and subscribers station resemble in construction those described and shown in an application for Letters Patent liled heretofore by me, but dilter therefrom in certain features, adapting them to the system described in the present application.

The letter A indicates the non-conducting base of the switch-board, which may be made of wood or other suitable material. It has arranged upon its front a central metallic plate, D2, which, by a wire, d, is connected with a receiving-telephone, D, which is connected with a transmitter, D4, which is connected in turn with the ground through a battery, B2.

In a circle around the central plate, D, ou the switch-board are arranged a series of individually-insulated metallic plates, indicated by the numbers l l', 2 2. 3 4 4', 85e. These plates are connected with the central-office terminals ofthe subscribers lines, respectively, those designated by simple numbers, as 1, being connected with the lines used for calling', and normally kept in connection with the calling-operators instruments at the central office,

(No model.)

while those designated by numbers marked thus as l', are connected with the line-wires, which are normally left open and only used when placed in electrical connection with the other wires for the purpose ot' completing metallic circuits. Each of these switch-board terminal plates is provided with a plug-socket, S, and each of the calling-wire terminal plates l 2 3 4, 85e., is provided also with an attached connector, O, each connect-or being provided with a plug, c, which lits all the sockets ofthe board. The connector O is made ot' a vmetallic spring strip or wire doubled in the form of a letter U, and has one leg in swiveling connection with the block, while the other leg is slightly shorter and provided with a plug of such size -that it will be held by friction in any of the switch-board plu g-sockets. The connector may be constructed to be held in place by a springcatch or a projecting pin, so that a special movement will be required-such as depressing the spring-catch or turning the connectingplug to the righ't or leftto remove the connector, thus preventing the removal of the connector and breaking the circuit by accident. When constructed in the manner mentioned the apertures in the terminal pieces and in the ring B will have to conform thereto, as in Figs. 25 and 4.

In Fig. 3 the connector C has a pin, c', projecting from the plug, and the terminal plate l husa slot, c2, extending from its socket, and

its wall undercut to permit the plug to be turned laterally to engage the pin with the catch thus formed.

In Fig. 4 the connector O2 is provided with a spring-catch, c3, which will take under a shoulder formed in the terminal plate. The ring B will have its sockets also modified as those of the terminal plates. The connector may be easily liexed, so that its plug may be inserted to form the connections hereinafter described, and itwill resume its normal shape and position when the plug is released. The precise shape ot' the connectoris not material, the main object being to haveit of such shape and resilience that it will stand out from the board and resulne its position when left free Outside of the circle of terminal plates isroo arranged a metal ring, B, which is provided with a plug-socket, S', opposite each ofthe calling-wire terminal plates, and said ring is connected by a wire, b, with a call-opcrators receiving-telephone, B', which is connected with a transmitter, B2, in the usual manner, and the transmitter is connected with the ground.

Surroundingthe ring B, and insulated therefrom, is another metallic ring, D, which is connccted with the central plate, D2, by a wire, d?. (Indicated by a dotted line.)

The several calling-wire terminal blocks, l 2 3 4, &c., are respectively connected with the coils ot' magnets N' N2 N3 N4 and so on, these coils being also included in the subscribers' lilies when the complete metallic circuits are established for the purpose of indicating to the switch-board operator when the Ylines to which they are connected are in use, and thereby obviate the necessity oll his connecting his telephone with any line in order to ascertain if it be in use or if conversation has been discontinued over two lines which have been connected. Il' any line is in use the magnet connected ill that line will attract its armature, owing to its being, when connected, in circuit with the subscriber-s battery, as will presently appear. y

The letters w w' 102 'w3 104 105, Snc., indicate the terminals of the lines connecting with the terminal plates ot" the switchboard. The wire w connects the terminal pla-te l with one terminal of the coils ol' indicating-magnet N', the other terminal of said coils being connected with the subscriber's callingwire W, leading to suhscribers station No. l," which is so marked on the drawings. At the subscribers station the line W divides at the point marked y, one branch, H, leading' to the receiver 1t, and connected therewithin amanner presently to be described, while the other branch, H', leads through the transmitter T and connects with one pole of the station-battery G, from the other pole ol' which a wire, g, leads to the receiver.

The receiver R has attached to its case a laterally-projecting tube, R', of insulating material, within which are two pairs of metallic and preferably elastic lingers, r r' and r2 r3, the pair of lingers r 1" projecting toward the middle of the tube from the opposite end. In the space between the ends ot' the two pairs ot' lingers is a loose metallic ball, M, and when the tube R' extends upward with respect to the case of the receiver, as shown in the ligure, the metallic ball M will rest upon a-nd electrically connect the lingers r2 r3; but if the tube 1t be reversed the ball will rest upon and connect the lingers i' r'.

The branch H of the calling-line wire'con.

nects with the tinger r2, and from the linger r3 a wire, I', connects with one terminal ol' the coils ol the bell-magnet K, from the other terminal ol' which a wire, l', leads to ground.

When the receiver R and tube R' are in the position shown in the drawings, which is their norma-l position when hung up and not in use, it will be observed that the line-wire \V is connected to ground through branch H,tinger r2. ball M, finger r, wire I, bell-magnet coils,and wire I', so that the subscriber may receive a call through his bell when a current is sent over his line-wire.

The wire g, which eonnectswith the branch H' through battery G and transmitter T, is connected with the linger i', while from a linger, i", a wire, g', leads to one terminal ot' the coil ol the receiver-magnet, (not show11,) and from the other' terminal ot' said coil a wire, g2, connects with wire I', and through it to ground. It will be seen that it' the position of the receiver be reversed from that shown in the drawings, as before described, the hall M will connect the lingers o' and r', and the line \V will be connected to ground through branch H', the transmitter T, battery Gr, wire g, linger r, ball M, linger 1^', wire g', receivercoihwire g2, and a part of wire l',the station apparatus heilig thus in condition l'or holding conversa tion with the central oflice or calling. At the same time the bell-magnet will be cnt out ol' circuit, as the lingers r2 and 1' are not connected. At this time, also, the current from the battery G traverses the calling-wire and charges the magnet N at the central ollice, which, by its action upon its armature, gives notice to the switch-board operator that the line is in use.

At the central ollice the plugs c of the connectors C are kept normally in the sockets S', behind their respective plates 1 2 3 4, &c. The line-wire W', which is normally open, leads from the switch-board terminal plate l' tothe subscriber's station, and there connects with the wire g2, between the receiver-coil and the ground. When a subscriber-say, iorinstance, subscriber No. l-wishes to communicate with another subscribersay subscriber No. 3--the rst puts his apparatus in condition for use, as justdescribed, the circuit being completed from his battery over his line-wire W', coils of magnet N', terminal plate lat switch-board,its connector G,metallicringB,wire b,and through the call-operators instrument to ground. He then informs the call-operator with whom he wishes to communicate, and the call-operator thereupon directs the.v switch-board operator to connectsubscribers7 lines land 3. The switchboard operator then first calls up subscriber No. 3. This he does by removing the plug of the connector C ot' terminal plate 3 from its socket in ring B,and placing said plug in contact with the central plate, Dzror ring D, thus connecting the subscribers line No. 3 with the ground through the connector O,plate D2 orring D, wire d, the switch-operatoi"s instruments, and battery B2. The current ot' battery Bllows over the line No.3 and rings the bell at the subscriber's station. \Vhen the subscriber No. 3 replies,and signilies through the switchboard-.opcra-tol 7s instrument that he is ready, the switch- IOO IIC

board operator proceeds to connect thetwo'subscribers in acomplete metallic circuit. This he does by first disconnecting the connection of plate l from the ringB and connectingit with plate 3', and then connecting the connector of plate 3 with plate l. By now following the conductors it will be found that the circuit leads from, say, battery G at station No. 1, through the transmitter T over branch H', calling-line wire W, plate l at switch-board, and its connector to plate 3', and thence over line-wire W5, to station-No. 3, and said line being there connected in the same manner that line Wis connectedat station No. 1, the circuit is continued over wires g2 g r M r g, through the station battery and transmitter, and over branch H of calling-line W4, and thence over the said line W4 to the central office, and then over plate3 and its connector to plate l', thence back to station No. 1, and over the wires g2 g r" M r g at that station to the opposite pole of the battery Gr from which it started.

1t will be understood that in the above description ot' the complete metallicucircuit the receivers at the stations are supposed to be in a position the reverse of that shown in the drawings, and the lingers r and r therefore connected by the ball M. There are various oth erarran'gements ofthe connections by which a normally-grounded calling-wire and a normally-open circuit-wire may be combined so as to form a' metallic circuit for a talking-circuit without departing from the spirit ot' my invention.

Instead of making the connections as heretofore described, the return-wire may be connected with the subscribers transmitter in such manner that by means otan automaticallyoperating switch the impulses ofthe transmitswitching device it may be cut out77 when not in use, and a bell cut in77 to give him notice of a call. Y

Having thus described-my invention,what I claim is- 1.. In a telephone-exchange system, the comnals being connected with one line through the 'secondary coil of the transmitter, and said battery and the otherterminal being connected totheotherlne-wireand also to groundthrough the magnet-coil ofthe receiver, and an automatic shuntingdevice arranged to connect said terminals when the receiver is held in position for use and to break connection between the same when hung or heldin a different position, substantially as described.

3. The switch-board having the terminal platesv arranged in a crcle,iu combination with aseries of subscribers circuits, each composed of two line-wires, the two terminal plates of each circuit being side by side, and each provided with a plug-socket and a iexible connector carrying a plug, substantially as described.

In testimony whereof I have hereunto set my hand in the presence ot' two subscribing witnesses.

C. A. RANDALL.

Witnesses:

F. A. KINSMAN, WM. THARP. 

